1. Technical Field
The present invention relates to the technical field of a magnetic field measurement apparatus, a magnetic field measurement system and a magnetic field measurement method.
2. Related Art
A magnetic sensor using optical pumping is used for a magnetic field measurement apparatus or the like which measures a magnetic field which is generated from a living body. The magnetic sensor includes a cell which is filled with an atom such as alkali metal in a gaseous state. When pump light which has a circular polarization component is irradiated to the cell, the filled atom is excited. Subsequently, when probe light which has a linear polarization component is irradiated so as to cross the pump light, the excited atom rotates the polarization surface of the linearly polarized light which is included in the probe light in response to a magnetic field which is applied from the outside. The magnetic sensor measures the magnetic field by measuring a rotational angle of the polarization surface of the probe light which has passed through the cell.
However, in a case of measuring a particular weak magnetic field such as a magnetic field, which is generated from the inside of a living body, by the magnetic field measurement apparatus, there is a problem in that the magnetic field from the outside of the living body may affect the measurement.
As techniques which cancel the external magnetic field, techniques which infer and cancel a disturbing magnetic field on the basis of the amount of the magnetic field which is measured using a magnetic sensor are disclosed in JP-A-2008-282983, JP-A-2003-332781 and JP-A-2000-329836. In addition, in JP-A-2007-170880 and JP-A-2001-51035, a gradiometric magnetic sensor, which cancels the influence of the magnetic fields which are not from the target to be measured and would become noise, by measuring gradient polarization components thereof using a plurality of coils, is disclosed.